Impressing systems comprising die plates mounted on a die holder are utilized to process and finish predetermined patterns in sheet-like material typically found in web or blank form. Typical die plates include perforating plates, scoring plates, embossing plates, cutting plates and the like. The die plates may be magnetically attached to the die holder which brings the plate into successive contact with the web or blank which advance on a conveyor system. The die plate must be accurately positioned on the die holder at a predetermined position to accurately engage the web or blank.
U.S. Pat. No. 4,823,659 to Falasconi, for example, describes a specific embodiment of an impressing system comprising a conventional rotary panel cutting apparatus for cutting windows, notches, cavities, orifices or other patterns in relatively thin, flexible sheet-like material typically found in either sheet or web form. The cutting apparatus may be used to produce envelopes having a transparent panel or window for allowing visual inspection of the enclosure. The window envelopes are manufactured from a web of material or from previously cut blanks having a predetermined shape. A panel is subsequently cut from the blank to form the window. A transparent material may be added to cover the window. The bank may be gummed, folded, printed and packaged to form the finished envelope.
The cutting apparatus comprises a cutting tool in the form of a cutting plate or die which may be magnetically mounted on a rotary die holder which brings the cutting die into successive contact with the web and the blanks which advance on a conveyor system. The cutting die has a raised cutting surface which is adapted to engage the paper and cut a pattern in the material. The die holder, sometimes called a die cylinder or drum, is mounted for rotation on a drive shaft synchronized with the conveyor system so that the cutting die engages a different blank for each rotation of the die holder at a specific predetermined location.
In the impression system, the die plate must be accurately aligned and positioned at a predetermined position along both the radial and circumferential axis of the die holder in order to insure that the die plate accurately and repeatedly engages the web blank. In order to position the die plate on the die holder in conventional systems, the leading edge of the die plate is typically disposed along a single leading edge reference mark disposed on the die holder.
Rotary impression system apparatus typically utilize one of a "straight" or an "angular" alignment system. Envelope rotary cutting apparatus, for example, include the "angular" based rotary cutting die systems made by F. L. Smithe Company.TM. and the like and "straight" based cutting die system made by Winkler and Dunibier Company.TM. and the like. In the straight system, when the leading edge of the cutting die is positioned along the die holder leading edge, the leading cutting surface of the cutting die is typically parallel to or horizontally aligned with the longitudinal axis of the die holder and a zero degree angle is formed relative to the longitudinal axis of the die holder. In contrast, in angular systems, when the leading edge of the cutting die is positioned along the die holder leading edge, the leading cutting surface of the cutting die is angularly aligned relative to the longitudinal axis of the holder. Different cutting systems will have different angular orientations, typically from about 0 to about 15.degree. in either direction, and preferably at a 11/2 degree.
Operators are thus required to maintain separate dies for each of the straight and the angular systems. An operator making a certain pattern will thus require two separate die plates when the impression operation is performed on both the angular and the straight systems. This has resulted in a relatively expensive duplication of inventory of die plates.